Cloth simulation acting wonky in render. Correct in viewport
It would be nice to see what it is doing in the final render. However, normally when something like this happens, either you have a subdivision surface modifier on the object with cloth and you have settings set differently on the view port than the render. This would apply into the same concept as other modifiers that you could have on the object with cloth simulation. It does not sound like subsurface. But, works the same depending on the mod. Obviously, something that is checked on for render in your scene and is set different to view port is affecting your final results.